1. Field of the Invention
The present invention relates generally to pipe couplings for fluid piping systems, and more particularly, to compression type couplings utilizing a gripper ring and sealing gasket where the gripper ring is prevented from locking the coupling in place before the seal is properly engaged.
2. Description of Related Art
In most fluid piping systems, couplings for pipe ends are employed in the construction of the system. As such, the overall reliability of the piping system often depends on the stability of the couplings used throughout the system. Accordingly, a number of different arrangements have been developed in an attempt to provide secure couplings between pipe ends. It is known to employ gripping members in order to prevent uncoupling of the pipe joints by longitudinal forces imposed on the coupled pipe sections. Other arrangements include a combination of rings and seals employed with compression type connections to hold pipe systems together. For example, a gland and gripping ring may be used in combination to position, compress, and seal a gasket about a pipe.
While the degree of pipe restraint on a coupled joint is critical, it is equally critical that an adequate gasket compression be achieved about the coupled pipe to insure a correct seal against leaks in the piping system. Accordingly, typical bolt type couplings having a gasket to effect sealing and a lock ring to restrain the coupled pipe against pull out are often utilized. In these couplings, a gripping ring is imposed on the pipe between the lock ring and the gasket to operationally grip the pipe prior to or simultaneous with compression of the gasket. The drawbacks of such couplings, however, are that they can result in an undetectable but inadequate gasket seal because the gripping ring often engages the pipe and locks it into place before the seal is properly actuated.
Accordingly, other compression couplings have been designed with various arrangements and parts to prevent gripper ring lock up prior to compression of the sealing gasket. For example, U.S. Pat. No. 4,569,542 discloses a bolt type coupling designed to provide clearance functions, so that gasket compression is achieved before the gripper ring effectively grips the pipe and locks the coupling in place when the bolt fasteners are tightened. U.S. Pat. No. 5,803,513, on the other hand, discloses the use of a plurality of skid pads strategically placed over the teeth of the gripping ring to prevent it from prematurely engaging the pipe before the compression of the accompanying gasket. While the couplings disclosed by U.S. Pat. Nos. 4,569,542 and 5,803,513 are useful for their intended purpose, they require additional or complicated arrangements of parts which may increase cost and/or hinder the ease of coupling installation.
What is needed then is a pipe coupling that is inexpensive and easy to install yet prevents the gripper ring from locking the coupling in place before the seal is properly engaged. It is to such a coupling that the present invention is primarily directed.